WASHINGTON (Reuters) - Vaccinations against the H1N1 swine flu virus began in the United States this week as part of the Obama administration's mass immunization effort to help limit the worst effects of the pandemic.
The U.S. Centers for Disease Control and Prevention expects up to 7 million doses of vaccine by the end of this week, mainly AstraZeneca unit MedImmune's nasal spray.
The U.S. government has ordered vaccine from five companies: Sanofi-Aventis SA, CSL Ltd, Novartis AG, GlaxoSmithKline and MedImmune.
Here are some questions and answers about the immunization program:
Vaccine production is expected to reach 40 million doses by mid- to late-October and continue to rise at a rate of about 20 million per week through December. The U.S. government has ordered 250 million doses and says this should be enough to ensure coverage for every American who wants it.
The CDC is working with healthcare services firm McKesson Corp. to distribute doses to 90,000 vaccination sites designated by state and local health departments. The sites include clinics, doctor's offices, hospitals, schools and retail chains where vaccine will be available.
The government says its centralized distribution system can reach more sites than the direct manufacturer distribution used for seasonal flu vaccine.
The United States hopes to vaccinate 160 million Americans considered at highest risk of death or severe disease by the beginning of December. These include pregnant women, people with asthma, diabetes or heart disease, and children and young adults.
The United States has also offered 10 percent of its vaccine supply, or about 25 million doses, to help the World Health Organization distribute vaccine to less developed countries.
The vaccine has taken less than a week to arrive at designated sites after orders are placed.
On Tuesday, health officials said the 50 U.S. states had ordered 2.2 million vaccine doses, or more than 90 percent of the 2.4 million doses currently available. Limited vaccination started on Monday.
U.S. health officials and other experts say some states may not have finalized their immunization programs while others are limited by constraints on budgets or storage capacity. State and local health departments also are still administering seasonal flu vaccinations, which became available earlier than usual this year.
The Health and Human Services Department expects orders to increase as vaccine becomes available in the more widely used injectable form.
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The federal government has spent or set aside $6.4 billion for H1N1 immunization so far. About $1.5 billion is for enough bulk antigen to create over 250 million vaccine doses, according to official statistics. The sum also includes $1.4 billion to help states and hospitals plan and prepare for the vaccination campaign.
Congress appropriated $7.65 billion in June for H1N1 and other pandemic influenza preparedness.
Editing by Cynthia Osterman